发表机构
University of Illinois Chicago（伊利诺伊大学芝加哥分校）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
针对现有拜占庭因果可靠广播协议元数据开销线性增长的问题，本文通过修改Bracha算法，提出首个常数元数据开销（O(1)）且通信复杂度为O(n²)的BCRB算法，容忍f<n/3拜占庭故障。
AI 中文摘要
异步拜占庭可靠广播（BRB）是一种基础原语，用于在存在拜占庭故障的分布式系统中保证一致性和有效性，但它缺乏排序保证。因果消息排序对于区块链和社交网络等许多应用非常重要。现有的拜占庭因果可靠广播（BCRB）解决方案存在若干缺点。此类协议通常将向量时钟或依赖屏障附加到应用消息上，导致元数据开销随系统进程数 $n$ 线性增长。在本文中，我们提出了首个保证安全性的最优消息开销 BCRB 算法。我们通过对 Bracha 的 BRB 算法进行相对较小但关键的修改来实现这一点，并证明我们的算法以最优消息元数据解决 BCRB。该算法实现常数大小 $\mathcal{O}(1)$ 的消息元数据开销和 $\mathcal{O}(n^2)$ 条消息，从而产生 $\mathcal{O}(n^2)$ 的通信字复杂度。相比之下，现有协议的通信字复杂度为 $\mathcal{O}(n^3)$。该算法容忍 $f < n/3$ 个拜占庭进程，这是众所周知的弹性最优界限，并使用四个阶段。
英文摘要
Asynchronous Byzantine Reliable Broadcast (BRB) is a fundamental primitive that guarantees agreement and validity in distributed systems subject to Byzantine faults, but it lacks ordering guarantees. Causal message ordering is important for many applications such as blockchain and social networking. Existing solutions for Byzantine Causal Reliable Broadcast (BCRB) have several drawbacks. Such protocols typically append vector clocks or dependency barriers to application messages, resulting in a metadata overhead that scales linearly with $n$, the number of processes in the system. In this paper, we propose the first optimal message overhead BCRB algorithm that guarantees safety. We do this by re-engineering Bracha's BRB algorithm with relatively small but critical modifications, and prove that our algorithm solves BCRB with optimal message metadata. The algorithm achieves constant-size $\mathcal{O}(1)$ message metadata overhead and $\mathcal{O}(n^2)$ messages, resulting in $\mathcal{O}(n^2)$ communication word complexity. This is as against $\mathcal{O}(n^3)$ communication word complexity of existing protocols. The algorithm tolerates $f < n/3$ Byzantine processes, which is the well-known optimal resilience bound, and uses four phases.
